Under this grant support several studies now underway will be pursued and new proposals started in the Hematology Research Laboratories of CMGH - all basically related to erythrocyte production and destruction. Rate of sickling and decrease of filterability (millipore) under conditions approximating physiologic changes. Production of vitamin B12 deficiency in the monkey: hematologic, biochemical alterations, combined system degeneration and amblyopia; relationship to chronic cyanide toxicity. Mechanism of production and significance of below normal vitamin B12 levels in pregnancy; interrelationships with folate, intrinsic factor, and B12 transport mechanism. Alterations in B6 metabolism in pregnancy and pyridoxal phosphokinase cellular activity. Estimation of minimum maintencance B6 and pyridoxal phosphokinase capacities in pyridoxine responsive anemia. Mitochondrial metabolism, pyridoxal phosphate content, pyridoxal- phosphokinase activity and aminolevulinic acid synthetase activity in developing red cells of sideroblastic anemias.